1. Field of the Invention
The present invention generally relates to storage technology and, more specifically, to technology for reducing the power consumption of a storage system, which stores a database (hereinafter “DB”).
2. Description of the Related Art
Numerous DB-based applications exist today, and database management systems (hereinafter, “DBMS”), which perform sequential processing and management operations related to DB, have become extremely important. One characteristic feature of a DB is the fact that it handles large volumes of data. For this reason, in most computer systems that operate a DBMS (hereinafter, also referred to as a DB system), it is common to have a system configuration such that a storage system, which comprises a plurality of storage devices (in other words, a large capacity storage system), is connected to the computer that operates the DBMS (hereinafter, also referred to as a DB server), and stores DB data in this storage system.
As the amount of DB data is increasing, in line with this, the capacity of storage systems is also expanding. Storage devices mounted in a storage system, for example, include magnetic tape devices, and storage devices capable of loading a disk (for example, a hard disk and a DVD (Digital Versatile Disks) (hereinafter, abbreviated as a “disk device”). Usually, infrequently accessed data (for example, archived data) is being stored on magnetic tape devices, which are less expensive than disk devices. However, as disk devices becoming less costly, archived data and other infrequently accessed data is increasingly being stored on disk devices.
One method for increasing the capacity of a storage system is to increase the number of disk devices mounted thereto. However, because of the large amounts of power consumed by the rotating disk drives, the power consumption of the storage system as a whole increases due to the addition of more disk storage devices. Technology for controlling power consumption, for example, is disclosed in Japanese Laid-open Patent No. 9-282057 (hereinafter, Document 1) and Japanese Laid-open Patent No. 2000-293314 (hereinafter, Document 2).
The technology disclosed in Document 1 controls the power saving of a disk device (ON/OFF of power supply or selection of power saving mode) in a disk array system after the passage of a pre-established period of time following an access from a host machine. Further, if the power supply of the access destination disk device is OFF when there is an access from a host machine, access is executed subsequent to the power supply of this disk device being turned back ON.
The technology disclosed in Document 2 is technology for controlling the power supply of devices targeted for power supply control, which make up a computer system including peripheral equipment. A job is executed in a computer system, and a system power supply control device prepares a power supply control plan for each device targeted for power supply control based on a job execution plan and operational results, and, in accordance with the prepared power supply control plan, controls the power supply of the devices targeted for power supply control corresponding to the aforesaid power supply control plan.
As described hereinabove, because ever increasing numbers of disk devices are being mounted to storage systems configured for storing DB data, there is a need for technology for reducing the power consumption of such storage systems.
As technology for reducing the power consumption of a storage system, technology, which uses the technique disclosed in Document 1, for example, a technique whereby the power supply to a disk device is turned OFF, and when there is an access, the power supply to this access destination disk device is turned back ON, can be cited. However, one of the problems associated with this technique is that when a storage system receives a read request from a host machine, because the system is configured such that data is read out after the disk device power supply is turned back ON, the read response to the host machine becomes delayed.
Conversely, according to the technique disclosed in Document 2, because the computer system referred to in Document 2 corresponds to a DB system comprising a DB server and storage system, the devices targeted for power supply control are the DB server and storage system as a whole. For this reason, in the technology disclosed in Document 2, it is not possible to control the power supply of an individual disk device inside the storage system.
Even if the technology of Document 1 could be combined with the technology of Document 2, it would still not be possible to achieve both goals of reducing the power consumption of the entire storage system, and checking the degradation of the response rate of the storage system by controlling a disk device inside the storage system. This is because combining the technologies of Document 1 and Document 2 would only result in the power supply to the access destination disk drive being turned ON if it is OFF when the power supply to the storage system as a whole is ON, and an access is generated to the storage system.